This invention relates to a grinding machine of the type which essentially comprises a frame for the displacement of the grinding-wheel slide along the frame towards a workpiece to be ground which is carried by a sliding table.
Up to the present time, the workpiece to be ground has been supported between two centers mounted respectively in a headstock fitted with means for driving the workpiece in rotation and in a tailstock, the headstock being stationarily fixed in an invariable location on the sliding table and the tailstock being mounted on the same table at a location which is variable as a function of the length of the workpiece to be ground.
This conventional arrangement, however, is subject to disadvantages. In point of fact, the back center is mounted within the tailstock by means of a sliding sheath in order that it may be moved away from the center which is mounted within the headstock each time it proves necessary to remove one workpiece in order to replace it by another. The presence of this sliding sheath makes it necessary to give the tailstock larger overall dimensions than would be the case if the back center were permanently fitted directly within the tailstock. In consequence, interferences are liable to take place between the tailstock and the wheel slide, especially when this latter is inclined with respect to the direction of the sliding table. This results in the need to increase the minimum diameter corresponding to permissible wear of the grinding-wheel and consequently in higher operating costs.
Moreover, the movement of withdrawal of the back center at the time of a change of workpiece takes place in opposition to a powerful restoring spring and consequently with a relatively short length of travel. This means that the end of the workpiece which is mounted on the tailstock is well freed as a result of this movement; but in order to disengage the other end of the workpiece from the center, it is either necessary to subject it to a slight movement of axial translation or to displace the table to the corresponding extent. However, a limited amount of space is available between the ends of the workpiece and the two centers, which often proves to be a source of difficulty in the design and operation of automatic workpiece changers.